The present invention relates to a wheel which is particularly usable for roller skates, such as in-line roller skates.
The wheels of roller skates are usually constituted by a central hub, made of various materials, which comprises bearings and is rotatably associable at a pivot of the skate frame. A tread is formed on the hub.
In conventional skates it is known to use wheels whose tread is substantially smooth, providing optimum application for skating on smooth and dry surfaces.
U.S. Pat. No. 5,527,100 discloses a composite wheel for in-line skates. The wheel comprises a first central section made of a synthetic plastic material which has a low friction coefficient, and second sections, which are arranged laterally to the first central section and are made of a second synthetic plastic material having a higher friction coefficient.
The above wheel has a higher coefficient of sliding friction of the sides of the wheel on the ground thus improving the braking action which is performed by tilting the skates as in ice-skating. Such wheel construction however does not improve the grip of the wheel while rolling.
This can occur for example during lateral curving, a condition in which the balance of the skater becomes more unstable, especially if the skating surface is slippery or when skating off-road, where the skating surface can be an unpaved road, a wet track, a lawn and in any case a slippery terrain.
As a partial solution to these drawbacks, skates are known which are marketed under the "Spin" trade-name and use wheels which have a plurality of identical and uniformly distributed raised portions at the surfaces of the tread that lie laterally to the central surface.
However, the above wheel ensures a grip which is preset during design as a function of a hypothetical configuration of the skating terrain, which is therefore a compromise among the many situations that the skater may instead encounter.
Moreover, the provision of raised portions or protrusions which rise from the tread leads to another drawback: the protrusions in fact tend to wear rapidly due to friction on the ground, causing the lateral surface of the tread to soon become substantially smooth, with a consequent loss of all advantages in terms of grip.